Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61C—DENTISTRY; APPARATUS OR METHODS FOR ORAL OR DENTAL HYGIENE
  • A61C13/00—Dental prostheses; Making same
  • A61C13/08—Artificial teeth; Making same
  • A61C13/083—Porcelain or ceramic teeth
  • A61C13/0835—Ceramic coating on metallic body
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K6/00—Preparations for dentistry
  • A61K6/20—Protective coatings for natural or artificial teeth, e.g. sealings, dye coatings or varnish
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K6/00—Preparations for dentistry
  • A61K6/30—Compositions for temporarily or permanently fixing teeth or palates, e.g. primers for dental adhesives

Definitions

• the invention relates to a dental bonding agent composed of aluminum powder in an inert liquid organic carrier, to a process wherein said bonding agent is used to bond dental porcelain to a metal core, and to the dental restorations produced by said process.
• Dental restorations generally comprise a metal core or framework to which porcelain is bonded on the visible surfaces for esthetic reasons.
• gold has been the basic structural metal for preparing the core or framework.
• non-precious metal alloys which could be used in place of gold. Such compositions are illustrated, for example, by U.S. Pat. Nos.
• Suitable alloys are typically nickel or cobalt-based alloys, particularly, nickel-chromium alloys.
• This invention is directed to a bonding agent and to a method for bonding dental porcelain to a nickel-containing non-precious metal alloy framework.
• a strong bond is formed which is able to resist separation of the porcelain under far greater stresses than in the absence of bonding agent.
• the bonding agents of this invention can be used under less critical conditions than prior, similar bonding agents.
• the bonding agent of this invention is aluminum powder plus an inert liquid organic carrier.
• the method of the invention comprises: (a) applying to a surface of a cleaned nickel-containing metal core a coating of the bonding agent of the invention; (b) baking the coated metal core in a substantially inert atmosphere to a temperature and for a period of time sufficient to form an aluminide layer on the surface of said metal core; (c) cleaning the coated and baked surface; and (d) applying porcelain to the baked and cleaned surface and firing.
• the article of the invention is a dental restoration comprising a metal core with a porcelain coating wherein the porcelain is bonded to the metal core with the bonding agent of the invention.
• Schmick in U.S. Pat. No. 2,996,419, discloses a bonding agent for joining glass to glass which consists of powdered aluminum and a non-volatile silicone resin that decomposes during firing to leave a residue of silica.
• British Pat. No. 1,529,267 discloses a bonding agent for joining porcelain to a metal core for making dental restorations, wherein the bonding agent comprises powdered aluminum, powdered glass, and a volatile liquid silicone oil carrier.
• the bonding agent described in the British patent was marketed commercially substantially as described in the patent, and then in an improved version wherein the silicone oil carrier was replaced by propylene glycol.
• the aluminum is employed in the form of a finely divided powder which preferably has an average particle diameter below about 25 microns. While the exact particle size is not critical, most (e.g., at least about 90 percent) of the particles should be below 200 mesh in order for the bonding agent to have acceptable handling characteristics.
• the aluminum powder is employed in an inert liquid organic carrier.
• organic carriers include propylene glycol, glycerol, esters, ketones, liquid hydrocarbons, and other organic materials that will volatilize and will not react with either the aluminum or the metal core so as to interfere with the aluminiding reaction.
• the organic liquid is used in appropriate proportions so that the bonding agent can be applied by brushing, spraying or dipping. Exact proportions can be determined by routine experimentation, but will usually be found a liquid:powder weight ratio within the range of from about 1:2 to 5:1.
• the bonding agent composition can be prepared by simply mixing the carrier with the aluminum powder to form a slurry.
• the powder and carrier may be mixed just before use, or they may be pre-mixed.
• the metal core is thoroughly cleaned before the bonding agent is applied. Cleaning can be by conventional procedures such as scrubbing with abrasive, brushing, ultrasonic cleaning in water, or the like.
• the bonding agent is then applied in a thin coat over the metal, using a brush or a spatula, spraying, or dipping, to yield a coating about 1 to 2 mils thick.
• the coated metal core is then fired.
• Typical firing conditions are the following:
• the aluminum powder reacts with nickel in the metal core to form nickel aluminide.
• the coated metal core After the coated metal core has been fired, it is preferably ultrasonically cleaned in water to remove non-adhering materials. Care should be taken in this step to remove all non-adhering materials.
• the porcelain is applied to the bonding agent coated metal surface in any appropriate manner normally employed to coat metal surfaces in the absence of a bonding agent. Preferred methods are painting on with a brush or coating with a spatula. After application of the porcelain, the porcelain is fired at temperatures appropriate for the particular porcelain and metal employed. Thus, it may be carried out at any appropriate temperature range within the broader limits of from about 1600° F. to about 2000° F. Thereafter, additional coatings of porcelain may be applied and fired in a conventional manner to complete the production of the dental restoration in which a bond is formed between the metal and porcelain which is resistant to separation on application of mechanical stresses.
• the bonding agent compositions of this invention are adapted to be employed with nickel-containing metal alloys and porcelains which are suitable for use together in the absence of a bonding agent.
• Metal alloys for which the bonding agent compositions of the invention are useful are the nickel based alloys, particularly the nickel-chromium alloys. Representative alloys are found in the aforementioned patents and dental literature on non-precious metal alloys. Other nickel-containing alloys with which the bonding agent composition may be employed are available under various trade names. Still other alloys with which the bonding agent compositions are usefully employed are disclosed in U.S. Pat. No. 4,129,944, and in published European Patent Application No. 5013, published Oct. 31, 1979.
• the porcelain which is to be bonded to the dental alloy may be any porcelain appropriate to be employed with the alloy chosen.
• dental porcelain as known in the art and embraces dental glasses. They generally contain silicon oxide, aluminum oxide, potassium oxide, sodium oxide, and minor amounts of other oxides.
• the porcelain covering which is first applied to the metal is an opaque porcelain.
• An opaque porcelain reduces the tendency of the metal to be seen through the final coating.
• Opaque porcelains are available commercially and include in the oxide composition either zirconium oxide, tin oxide, titanium oxide, or zirconium silicate as an opaquing agent.
• the opaque porcelain is normally coated with a relatively thick layer or layers of body porcelain followed usually by a final layer or coating at the tips of incisal porcelain.
• the body porcelain is available commercially as gingival or body porcelain (sometimes called dentine) and may have a small amount of opaquing agent, and incisal porcelain is usually of similar composition as body porcelain without opaquing agent.
• porcelain is bonded to porcelain.
• porcelain is bonded to metal and the problems to be solved by the bonding agent composition of the present invention are with the porcelain-to-metal relationship.
• the porcelain which is to be bonded to metal is that understood in the art as opaque porcelain
• the porcelains which are to be bonded to metal by the bonding agent compositions usually are opaque porcelains, although not limited thereto.
• the selection of the procelain in terms of exact composition is dependent to a greater degree on the metal alloy substrate which is to be faced with the porcelain than on the bonding agent.
• the bonding agent to have the advantageous properties provided by the invention, it is expected that the selection of the procelain be appropiate for the metal alloy core or substrate employed.
• the thermal expansion properties of porcelain should be compatible or reasonably matched with that of the alloy. It is recognized that a meaningful single coefficient of expansion is not obtainable for porcelain as it is for metal over the broad temperature range of about 25° to 600° C. and that coefficients of expansion values are valid only for a narrow range of temperatures. Frequently, therefore, after preliminary determination of the coefficients of expansion, empirical methods are employed for the selection of the porcelain to be employed with the particular alloy.
• the method of selection of porcelain for use with a particular alloy is not part of the present invention, but when a reasonably "matched" porcelain and metal alloy are to be bonded together, the use of the bonding agent of this invention greatly enhances the bonding properties.
• a major advantage of the bonding agent of this invention is that the procedure for using it is relatively non-critical. Therefore, excellent results can be obtained more readily in the dental laboratory over a wider variety of conditions. The experiments discussed in this Example 1 demonstrate this advantage.
• CERAMALLOY II* flags (3 cm long ⁇ 1 cm wide ⁇ 0.5 mm thick) were investment cast and a 1 cm area in the center of the flag was roughened using a diamond handpiece in preparation for bonding agent application. All flags were ultrasonically cleaned in distilled water.
• Enough propylene glycol was mixed with aluminum powder so that the mix will drip easily from the spatula. A quantity just enough to cover the metal was brushed on.
• Powder and propylene glycol was mixed so that the mix gave a good paintable consistency and clung moderately to the spatula. An even coat was applied over the metal surface.
• Powder and propylene glycol were mixed so that the material clung strongly to the spatula. An even coat was applied over the metal surface.
• the flags were dried on the furnace door and inserted in the furnace at 1200° F., the furnace was evacuated and the furnace temperature was raised to 1550° F.; 1650° F.; 1750° F.; or 1850° F. at a rate of 100° F./min. Samples were removed from the furnace and bench cooled to room temperature.
• a standard opaque porcelain was applied and fired at 1200° F.-1700° F. under vacuum, 1700° F.-1850° F. in air, and bench cooled.
• Standard flexure adhesion test was used to determine the porcelain bonding characteristics. The test is described by W. J. O'Brien in a chapter entitled “Cohesive Plateau Theory of Porcelain-Alloy Bonding", in “Dental” "Porcelain”, edited by Yamada et al., University of Southern California (1977).
• Table III summarizes the flexure adhesion data to show the effect of bonding agent firing temperature on the percentage porcelain retention. These results show very little variation in the percentage porcelain retention data with firing temperature between 1550° F.-1850° l F.
• Alcoa 101 Powder is slightly coarser than Alcoa 123 Powder (See Table I). Therefore, in order to see any changes in percentage porcelain retention, Alcoa 101 was compared with Alcoa 123, using thin and medium coats, fired to 1550° F. The results are given in Table V.
• the foregoing Example illustrates the fact that the bonding agent of the invention can be employed over a wide range of conditions.
• the prior commercial bonding agent composed of aluminum powder, glass powder, and a carrier such as propylene glycol, had to be used under much more critical conditions.
• the minimum firing temperature was about 1750° F.
• the best firing temperature was even higher, e.g., about 1900° F.
• the thickness of the coating was also quite critical in that the range of thicknesses that had to be used to obtain adequate adhesion was quite small.
• a stiff brush had to be used to clean the fired coated metal in order to remove inadequately adhered and excess bonding agent.
• a thixotropic agent i.e., a material to impart thixotropy
• a thixotropic agent i.e., a material to impart thixotropy
• Such materials as colloidal silica, finely divided magnesium aluminum silicate, finely divided alumina, or other similar materials, can be added in small amounts (i.e., less than 1 weight percent and preferably less than 1/2 weight percent, based on weight of aluminum) to enhance the adhesion of the unfired bonding agent. At these low proportions, little, if any, effect on other properties is noted. A small amount of water can be used with the thixotropic agent to enhance its effect.

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• Health & Medical Sciences (AREA)
• Oral & Maxillofacial Surgery (AREA)
• Epidemiology (AREA)
• Life Sciences & Earth Sciences (AREA)
• Animal Behavior & Ethology (AREA)
• General Health & Medical Sciences (AREA)
• Public Health (AREA)
• Veterinary Medicine (AREA)
• Engineering & Computer Science (AREA)
• Ceramic Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Dentistry (AREA)
• Dental Preparations (AREA)
• Adhesives Or Adhesive Processes (AREA)
• Ceramic Products (AREA)

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Related Parent Applications (1)

Publications (1)

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Cited By (9)

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Citations (14)

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• 1982
  • 1982-11-10 US US06/440,231 patent/US4461618A/en not_active Expired - Lifetime
  • 1982-12-23 GR GR70169A patent/GR77047B/el unknown
• 1983
  • 1983-01-06 NZ NZ202963A patent/NZ202963A/xx unknown
  • 1983-01-21 ES ES519196A patent/ES8403021A1/es not_active Expired
  • 1983-01-24 BR BR8300338A patent/BR8300338A/pt unknown
  • 1983-01-24 PH PH28424A patent/PH19348A/en unknown
  • 1983-01-24 PT PT76135A patent/PT76135A/pt unknown
  • 1983-01-24 FI FI830223A patent/FI830223L/fi not_active Application Discontinuation
  • 1983-01-24 AU AU10721/83A patent/AU1072183A/en not_active Abandoned
  • 1983-01-24 NO NO830216A patent/NO830216L/no unknown
  • 1983-01-24 EP EP83300344A patent/EP0086575A3/en not_active Withdrawn
  • 1983-01-25 DK DK28883A patent/DK28883A/da not_active Application Discontinuation

Patent Citations (14)

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